1. Technical Field
An organic anti-reflective polymer is disclosed which prevents back reflection of lower film layers and eliminates standing waves that occur by changes in the thickness of photoresist and by light, during a process for forming ultrafine patterns that use photoresist for lithography by using 193 nm ArF. A method of preparing the organic anti-reflective polymer is disclosed as well. More particularly, the disclosed organic anti-reflective polymer is useful for forming ultrafine patterns of 64M, 256M, 1G, and 4G DRAM semiconductor devices. A composition is also disclosed comprising such an organic anti-reflective polymer, an anti-reflective coating therefrom and a preparation method thereof.
2. Description of the Related Art
During a submicrolithographic process, one of the most important processes for fabricating highly integrated semiconductor devices, standing waves inevitably occur and reflective notching of the waves results due to the optical properties of lower layers coated on the wafer and to the changes in the thickness of photosensitive film applied thereon. In addition, the submicrolithographic process generally suffers from a problem of the CD (critical dimension) alteration caused by diffracted and reflected light from the lower layers.
To overcome these problems, it has been proposed to introduce a film, called an anti-reflective coating (hereinafter sometimes referred to as xe2x80x9cARCxe2x80x9d), between the substrate and the photosensitive film, which prevents back reflection at the lower layer by introducing organic material having high absorbance at a wavelength range of the light employed as a light source.
Such anti-reflective coating is classified as xe2x80x9cinorganicxe2x80x9d or xe2x80x9corganicxe2x80x9d anti-reflective coatings depending upon the material used, or as xe2x80x9cabsorptivexe2x80x9d and xe2x80x9cinterferingxe2x80x9d anti-reflective coatings depending on the operation mechanism.
In conventional microlithography processes using I-line (365 nm wavelength) radiation, inorganic ARCs, for example TiN or amorphous carbon coatings, are employed when advantage is taken of an absorption mechanism, and SiON coatings are employed when an interference mechanism is employed. The SiON ARCs are also adapted for submicrolithographic processes which use KrF light sources.
However, in the above cases involving inorganic anti-reflective films mentioned above, a material to control interference of light at 193 nm is still required and, in recent years, there has been great deal of effort to apply an organic compound as the anti-reflective coating and/or film.
In view of the present development status, organic ARCs must satisfy the following fundamental requirements to be useful.
First, the peeling of the photoresist layer due to dissolution in solvents should not take place when conducting a lithographic process. In this regard, the organic ARCs materials have to be designed so that their cured films have a crosslinked structure without producing by-product.
Second, there should be no migration of chemical materials, such as acids or amines, into and from the ARCs. If acids are migrated from the ARCs, the photosensitive patterns are undercut while the egress of bases, such as amines, causes a footing phenomena.
Third, the etching rate of the ARCs should be faster than that of the upper photosensitive film, allowing an etching process to be conducted smoothly with photosensitive film serving as a mask.
Finally, the organic ARCs should be as thin as possible while playing an excellent role in preventing light reflection.
In recent years, studies have been carried and/or are in progress to develop novel organic anti-reflective films or materials which satisfy the requirements described above, while appropriately controlling the interference. As a result, a number of organic anti-reflective coating materials have been produced.
Such existing organic anti-reflective material is mainly divided into the following two types: (1) polymers containing chromophore, cross-linking agent (single molecule) for cross-linking the polymers and an additive (thermally variable oxidant); and (2) polymers which can cross-link by themselves and which contain chromophore and an additive (thermally variable oxidant). But these two types of anti-reflective material have a problem in that it is impossible to control the k value because the content of the chromophore is defined depending to the ratio originally determined at the time of polymerization, thus, it should be synthesized again if a change of the k value is required.
Accordingly, there is still an urgent need for novel organic anti-reflective material which can control the interference at the ArF wavelength of 193 nm, allowing the k value to be controlled easily only by a variation of reaction concentration.
A novel organic compound is disclosed which can be used as an anti-reflective coating using 193 nm ArF, 248 nm KrF and 157 nm F2 laser.
A method for preparing an organic compound is disclosed which prevents the diffusion and reflection caused by the light exposure in submicrolithography.
An ARC composition is disclosed which contains such a diffusion/reflection-preventive compound.
An ARC formed from such a composition and a preparation method therefore is also disclosed.